1. Field of the Invention
The present invention relates to a quantitative feeding apparatus usable for pulverized and/or granular material wherein an amount of pulverized and/or granular material to be supplemented is automatically controlled by measuring a predetermined amount of pulverized and/or granular material and the predetermined amount of pulverized and/or granular material is then mechanically fed to the outside. Further, the present invention relates to a master batch type multi-colored feeding apparatus using the quantitative feeding apparatus wherein a master batch comprising a number of colored pellets is fed to the lower part of a hopper for a mixer so that the colored plastic material is molded in a molding machine. In addition, the present invention relates to a runner recycling apparatus usable for reusing runners produced during a period in which injection molding is achieved using the quantitative feeding apparatus, more particularly, to a runner recycling apparatus which assures that changing of the kind of color or material to another one can be quickly executed.
2. Description of the Prior Art
Hitherto, a quantitative feeding apparatus for feeding a predetermined amount of pulverized and/or granular material has been used in a variety of industrial fields. It is typically used, for instance, for a pulverized material molding machine, a master batch type multi-colored automatic feeding apparatus usable for a plastic molding machine, a runner recycling apparatus or the like.
FIG. 8 schematically illustrates, by way of an example, a multi-colored feeding apparatus for a plastic molding machine in which a quantitative feeding apparatus usable for pulverized and/or granular material is incorporated.
Specifically, referring first to FIG. 8, reference numeral 101 designates a molding machine which is associated with a multi-colored feeding apparatus 102. In the multi-colored feeding apparatus 102, a master batch is supplemented to a quantitative feeding apparatus 104 from a master batch storage hopper 103. The quantitative feeding apparatus 104 is adapted to feed a predetermined amount of master batch to a master batch receiving hopper 106 by operating a feeder 105. The master batch is delivered to a mixer 108 from the master batch receiving hopper 106 via a piping 107' by means of a pneumatic conveyor 107 so that it is mixed with natural resin delivered from a natural resin hopper 111 in the mixer 108. Thereafter, a raw material thus prepared is fed to the molding machine 101 via a raw material feeding port 112.
As to the quantitative feeding apparatus used in that way, many types are well known such as a belt feeder type, a table feeder type, a rotary feeder type, a vibrative feeder type, a screw feeder type, a spring feeder type or the like.
On the other hand, a step of mixing in accordance with the master batch system during plastic molding operation is practiced in such a manner that natural resin and master batch are mixed with each other in a batch type using a mixer such as tumbler, Henschel mixer or the like and thereafter a mixture thus prepared is introduced into a hopper for the molding machine. However, in the case where mixing is achieved in a batch type, a period of several hours is required for cleaning the mixer used for practicing the above-described mixing system when the kind of color is changed to another one, which provides a significant hindrance which has an adverse effect on smooth progress of the steps. In addition, separation of natural resin from the master batch takes place due to static electricity generated by vibrating or flowing of material in the hopper for the molding machine. This leads to the drawback that a final product in which additives such as pigment, dispersant or the like in the master batch are uniformly distributed can not be obtained.
To improve the above-described method or mixing in a batch type, automation has been carried out with respect to measuring and mixing and various systems have been put in practical use.
Now, these systems will be described with reference to drawings which schematically illustrate apparatus which are employed at present.
One of them is an apparatus as shown in FIG. 9 which is so constructed that a mixer 108 is disposed above a raw material feeding port 112 for a molding machine 101 and the mixer 108 is separately provided with a quantitative feeding apparatus 113 usable for natural resin and a quantitative feeding apparatus 114 for master batch. The other one is an apparatus as shown in FIG. 10 which is so constructed that a mixer 108, a quantitative feeding apparatus 114 usable for master batch and a quantitative feeding apparatus 13 usable for natural resin are disposed one above another. However, since each apparatus is constructed in a batch type and they are arranged above the molding machine, disassembling and cleaning are very troublesome when the kind of color is to be changed to another one and moreover an occurrence of separation in the hopper for the molding machine as mentioned above can not be prevented. In recent years, there has been raised a requirement for increasing a concentration of pigment in the master batch to such an extent that a weight ratio of master batch to be added to natural resin is set lower than 3/100. Consequently, a correct mixing accuracy can not be maintained as far as a micro part in the mixture is concerned. In addition, an apparatus as shown in FIG. 11 is known which is so constructed that a quantitative feeding apparatus 114 usable for master batch is provided above a molding machine 101 and the master batch is quantitatively fed to a raw material feeding part for the molding machine so that it is mixed with natural resin which is fed from a hopper 115 separately disposed for the molding machine. However, this type of apparatus has also a drawback that disassembling and cleaning are inconveniently achieved because the quantitative feeding apparatus is arranged above the molding machine. Additionally, in a case where a method of measuring a master batch is of volumetric type in connection with the examples shown in FIGS. 9, 10 and 11, the quantitative feeding apparatus has drawbacks that such a malfunction that incorrect pellets are contained in the master batch or no pellet is fed for an unidentified reason can not be detected and any fluctuation in apparent density of the master batch can not be compensated satisfactorily. Accordingly, the drawback inherent in the volumetric type can be eliminated by allowing the method of measuring to be changed to a weight type but arrangement of a new apparatus on the mixer renders the quantitative feeding apparatus more complicated. Thus, the more complicated the quantitative feeding apparatus, the more troublesome are disassembling and cleaning operations.
To overcome the problems appearing in automatic feeding of a master batch, the inventor proposed a master batch type automatic feeding apparatus as disclosed in an official gazette of Japanese Laid-Open Patent No. 110411/1985. As shown in FIG. 8, the proposed master batch type automatic feeding apparatus comprises a master batch storage hopper 103, a quantitative feeding apparatus 104, a pneumatic conveyor 107, a cyclone 109 and a mixer 108. Further, as shown in FIG. 12, to assure that various kinds of molded products can be produced using different master batches, the same number of master batch storage hoppers 103a to 103e and quantitative feeding apparatus 104a to 104e as the number of kinds of materials are provided so that an arbitrary master batch can be fed to the molding machine merely by shifting switches. By doing so, separation of natural resin from the master batch in the hopper for molding machine does not take place. Accordingly, molded products to be rejected are not produced and thereby it becomes possible to produce molded products excellent in quality and stability. Additionally, when the kind of master batch or color is to be changed to another one, time and manhours required for cleaning the apparatus can be minimized whereby a master batch type automatic feeding apparatus which is very effective in production with many kinds and small quantity can be provided.
With respect to the quantitative feeding apparatus, a single quantitative feeding apparatus is hitherto used for the purpose of feeding just a single kind of raw material. However, in recent years, there is a tendency for production to be achieved in a fashion of many kinds and small quantity while a minimized amount of inventory is maintained. This causes a single quantitative feeding apparatus to be used for feeding many kinds of materials after disassembling and cleaning it, and a time interval required for changing the kind of material to another one tends to be shortened gradually.
Accordingly, properties of the quantitative feeding apparatus relating to disassembling and cleaning thereof have a significant effect on productivity. As to the kind of conventionally used quantitative feeding apparatus, there are known many kinds or types such as a belt feeder type, a table feeder type, a rotary feeder type, a vibrative feeder type, a screw feeder type, a spring feeder type or the like and each of them is properly used dependent on their utilization fields. However, a problem is that it is difficult to clean them without disassembling with the exception of the belt feeder type and the vibrative feeder type. The vibrative feeder type quantitative feeding apparatus is excellent in cleanability but in view of the current tendency that the quantitative feeding apparatus is changed to a weight controlling type, vibration is problem when its weight is measured or detected.
When the belt feeder type quantitative feeding apparatus is employed, it is very simple and easy to clean its surface. Accordingly, it is advantageous when granular material is handled but in a case where pulverized material is handled, it is difficult to completely clean the inside of a belt or the dirty interior of a closed belt.
With respect to the quantitative feeding apparatus having another type of feeder incorporated therein, it is possible to control its weight but it is impossible to clean it without disassembling. Moreover, this type of quantitative feeding apparatus which is compact in structure is not known.
Next, with respect to the master batch type automatic feeding apparatus, there is a need for providing the same number of quantitative feeding apparatus as the number of kinds of materials to be handled, in order to product various kinds of molded products using different master batches. Accordingly, the apparatus offers significant drawbacks in that the apparatus is manufactured at an expensive cost and a wide space is required for installation of the apparatus.
As another example relative to the prior art, FIG. 13 schematically illustrates a runner recycling apparatus usable for a plastic molding machine, in which a quantitative feeding apparatus operable for pulverized and/or granular material is incorporated.
When plastic products are produced by employing an injection molding method, runners generated during injection molding operation are not thrown away as waste material but they are reused for the purpose of reducing production cost. This type of production system has been widely employed. Prior to reusing runners, they are crushed so that crushed runners are fed to a molding machine after they are mixed with new material in the form of pellet or powder. To this end, various kinds of apparatus have been hitherto put into practical use. For instance, an apparatus as shown in FIG. 13 is so constructed that a hopper 121 in which new material is stored and a crusher 122 for crushing runners are arranged in a side-by-side relationship, the hopper 121 and the crusher 122 are communicated with a piping 125 having a large diameter via a new material feeding port 123 and a crushed runner feeding port 124 and the one end of the piping 125 is connected to a hopper 127 located above a molding machine 126 while the other end of the same is connected to a blower 128. The new material is measured at every shot with the use of an air nozzle 129 disposed below the hopper 121 and it is then delivered to the piping 125 via the feeding port 123. On the other hand, runners conveyed by a conveyor 130 are introduced into the interior of a crusher 122, they are crushed by a plurality of crushing blades 131 in the crusher 122 and thereafter they are delivered to the piping 125 via the feeding port 124. New material and the crushed runner delivered into the piping 125 are mixed with each other while they are transferred through the piping 125 by operating the blower 128. Finally, a mixture thus prepared is fed to the hopper 127 disposed above the molding machine 126. Incidentally, reference numeral 132 designates driers which are disposed by the side of the hoppers 121 and 127.
On the other hand, a recycling apparatus as shown in FIG. 14 is similar to that in FIG. 13 with the exception that volumetric type measuring means 133 in the form of a rotary valve or the like is attached to each of the feeding port 123 for the new material hopper 121 and the feeding port 124 for the crusher 122. When new material and the crushed runner are delivered to the piping 125, they are measured by the measuring means 133.
As is apparent from the above description, each of the conventional runner recycling apparatus is commonly constructed such that the crusher 122 is provided with the crushed runner feeding port 124 at its lowermost end and thereby crushed runners which fall down under the effect of their natural gravity force are collected above the feeding port 124. With such construction, when the kind of color or material is to be changed to another one, it is necessary that the interior of the crusher 122 is cleaned after the feeding port 124 is disconnected from the piping 125 resulting in a problem of degraded operative properties arising. Particularly, in a case where measuring means 133 is disposed for the purpose of measurement (see FIG. 14), there is a need for carefully cleaning the measuring means 133 after the latter is disassembled. This leads to a problem that operative properties are degraded further.
In addition, due to a requirement that materials are mixed together in the piping 125 when the conventional runner recycling apparatus is employed, the piping 125 having a large diameter and the blower 128 designed in larger dimensions are required. Besides this, to assure that mixing is effected sufficiently in the piping, a length of the piping should be elongated. Thus, there arises another problem that a wide space required for installation of the piping should be reserved.